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Abstract

The Crusoe processor solutions consist of a hardware engine logically surrounded by a software layer. The engine is a very long instruction word (VLIW) CPU capable of executing up to four operations in each clock cycle. The VLIW's native instruction set bears no resemblance to the x86 instruction set; it has been designed purely for fast low power implementation using conventional CMOS fabrication. The surrounding software layer gives x86 programs the impression that they are running on x86 hardware. The software layer is called Code Morphing software because it dynamically "morphs" x86 instructions into VLIW instructions.

Description of Crusoe Processor

The Code Morphing software includes a number of advanced features to achieve good system-level performance. Code Morphing support facilities are also built into the underlying CPUs. In other words, the Transmeta designers have judiciously rendered some functions in hardware and some in software, according to the product design goals and constraints. Transmeta's Code Morphing technology changes the entire approach to designing microprocessors. By demonstrating that practical microprocessors can be implemented as hardware-software hybrids, Transmeta has dramatically expanded the design space that microprocessor designers can explore for optimum solutions. Upgrades to the software portion of a microprocessor can be rolled out independently from the chip. Finally, decoupling the hardware design from the system and application software that use it frees hardware designers to evolve and eventually replace their designs without perturbing legacy software.

The concept of Crusoe is well understood from the simple sketch of the proceesor architecture , called 'amoeba'.In this concept , the x86 architecture is an ill-defined amoeba containing features like segmentation, ASCII arithmetic ,variable-length instructions etc. The amoeba explained how a traditional microprocessor was, in their design, to be divided up into hardware and software.Thus Crusoe was conceptualised as a hybrid microprocessor , that is it has a software part and a hardware part with the software layer surrounding the hardware unit.The role of software is to act as an emulator to translate x86 binaries into native code at run time.

Crusoe is a 128-bit microprocessor fabricated using the CMOS process.The chip's design is based on a technique called VLIW to ensure design simplicity and high performance.Besides this it also uses Transmeta's two pateneted technologies , namely , Code Morphing Software and LongRun Power Management.It is a highly integrated processor available in different vesions for different market segments.